Detection of fish bones in cod fillets by UV illumination

Abstract

The presence of fish bones is now regarded as an important hazard in fishery products, and there is increasing demand for new analytical techniques to control it more effectively. Here, the fluorescent properties of cod bones under UV illumination were investigated, and the maximal wavelengths for excitation and emission were determined to be 320 nm and 515 nm, respectively, demonstrating significantly different fluorescence characteristics and much higher fluorescence intensity compared to those of fillet muscles. Based on the results, UV fluorescence-assisted candling for the detection of bones in fishery products was developed for the first time. Using cod fillets as samples, the detection ratio of this technique was calculated as 90.86%, significantly higher than that of traditional candling under daylight (76.78%). Moreover, the working efficiency of the new technique was about 26% higher than that of the traditional method. A UV fluorescence imaging framework was also developed, and a method for automatic identification of the fish bones in the cod fillets based on the linear discriminant analysis proposed by Fisher was preliminarily realized, but the detection ratio was demonstrated to be relatively poor compared to those of candling techniques. These results allow us to suggest UV-based methods as new and promising approaches for routine monitoring of bones in fishery products.